CCSDS图像无损压缩标准在恒速信道中的应用研究

在CCSDS建议的无损数据压缩的基本原理上 ,结合基于局域纹理特征的处理方法 ,给出数据输入输出在恒速信道条件下一种有效的面向空间应用的遥感图像无损压缩方案。该方案包括去相关处理、熵编码以及压缩缓存控制三部分。去相关操作是在局域纹理分析方法的基础上 ,通过提取两种有效的预测模型并自适应选择最佳的模型进行处理 ;然后采用快速有效的CCSDS熵编码器对最佳去相关模型的预测误差编码。在压缩方案中充分考虑了输入输出恒速信道条件下应用的特殊性 ,设计了相应的压缩码流控制方法 ,从而给出了一套有效的针对恒速输入输出信道条件下的图像无损压缩的应用方案     

微等离子体转化二氧化碳发射光谱诊断

火星大气层的主要成分为二氧化碳,如果能够利用低温等离子体方法高效分解二氧化碳,使其转化为氧气和一氧化碳加以利用,可以大幅降低航天员生命保障相关载荷长途运输的成本,进一步提高生命保障能力.低温等离子体放电过程中会产生大量活性组分,可以在数百度温度下实现二氧化碳的高效解离,是具有很大潜力的二氧化碳解离与转化方式.设计了一种...     

一种终端区利用率评估方法研究

终端区利用率量化评估是解决终端区运行瓶颈、挖掘运行潜力的重要前提。现有方法大都面向全空域,指标缺乏通用性。聚焦终端区运行特点,构建了终端区利用率评估指标,基于灰色绝对关联度和主成分分析法,建立了灰色主成分评估模型,并对传统灰色绝对关联度的计算方法进行改进。以20个典型终端区数据为基础,经模糊C均值聚类验证了所提方法有效正确,且可区分性更好,能够满足多个终端区间的横向对比要求;结合广州终端区雷达数据进一步分析,发现方法更加细致地反映了沿时间轴的资源利用情况,满足单个终端区的纵向对比要求,可以为终端区的天气影响评估及流量管理优化策略评估提供论证依据。     

Rician衰落信道下Turbo码性能分析

文中研究了Rician信道下Turbo码的性能,并详细推导Turbo码在Rician信道下的误码率上界的表达 式,最后对Rician信道的主要参数对译码性能的影响作了仿真。     

Location-aware channel estimation for capacity gains on multibeam satellite links

Bandwidth is an expensive and scarce resource, thus its efficient exploitation is of paramount importance. Recent communication satellites feature sophisticated spatial access strategies through spot beams providing this way a total throughput in the range of 100 Gbit/s. Next generations of communication satellites, as postulated in the Satellite Communications Network of Experts (SatNEx) III, a project funded by the European Space Agency (ESA) for advanced research in satellite communications, require technological developments to achieve the Tbit/s region. Multibeam architectures formed by a central gateway, a multibeam satellite, and an aggressive frequency reuse strategy can meet such ambitious design goals. Interference problems are tackled by appropriate countermeasures such as (joint) precoding and beamforming on the forward link as well as multi-user detection on the return link; these methods require accurate and timely knowledge of the channel state, which in turn necessitates suitable algorithms for channel estimation. This paper addresses performance issues related to channel state estimation on the symbol-synchronous forward link and the frame-synchronous return link. It highlights for both directions the potential performance gain by assuming a priori knowledge of the user position, in this context referred to as location-aware channel estimation.     

Prediction of horizontal gas–solid flows under different gravitational fields

In this paper the performance of horizontal pneumatic conveying under different gravity environments is evaluated. An Euler–Lagrange approach validated versus ground experiments is employed to predict the relevant particle variables such as particle mass flux, mean conveying and fluctuating velocities in terrestrial, lunar and micro-gravity conditions. Gravity reduced computations predict a reduction in the global particle–wall collision frequency. Also, in the case of low wall roughness and small particle mass loading, reduction of gravity acceleration implies an increase of particle–wall collision frequency with the upper wall of the channel affecting greatly the particle mass flux profile. In the case of high wall roughness and/or high particle-to-fluid mass loading (i.e., around 1.0) particle conveying characteristics are similar in the three gravity conditions evaluated. This is due to the fact that both, wall roughness and inter-particle collisions reduce gravitational settling. However, the influence of gravity on the additional pressure loss along the channel due to the conveying of the particles is much reduced.     

县域土地利用与生态环境关系探讨

以福建省云霄县作为探讨案例，根据存在的生态环境问题，并结合土地利用现状，提出创建环境友好型土地利用模式、大力加强生态建设、加强区域环境整治力度三点建议，从而探讨县域土地利用与生态环境协调发展的可行性。     

X波段遥感数传微波通道

遥感数传微波通道是数传遥感卫星的发射系统,是实现地物信息实时传输的重要设备。为了实现高码速率的传输,分别利用上边带上变频器和下边带上变频器将传输的微波信道分成两个信道,每个信道传输53Mbit/s,两个信道可传输的码速率为106Mbit/s。文章介绍了单信道微波通道和双信道微波通道,并扼要地介绍了微波通道中的上变频器和阶跃管电抗开关倍频器。     

信道状态信息无线感知数据获取及应用综述

近年来,基于信道状态信息（CSI）的无线感知技术在室内定位、活动识别、健康检测等方向有众多探索性研究应用。然而,现有研究获取CSI数据主要依靠自主采集,对CSI开源数据集和数据采集设备/工具的研究现状不够清晰。首先阐述了基于无线保真（WiFi）CSI的无线感知技术,详细介绍了9种CSI数据采集设备/工具,概括了CSI的应用方向及研究现状,并汇总了近5年的CSI开源数据集,分析了现有CSI无线感知研究的局限性与面临的挑战,最后总结全文并对CSI无线感知未来的发展进行展望。     

Online condition diagnosis for a two-stage gearbox machinery of an aerospace utilization system using an ensemble multi-fault features indexing approach

China manned space station is designed to operate for over ten years. Long-term and sustainable research on space science and technology will be conducted during its operation. The application payloads must meet the ‘‘long life and high reliability" mission requirement. Gearbox machinery is one of the essential devices in an aerospace utilization system, failure of which may lead to downtime loss even during some disastrous catastrophes. A fault diagnosis of gearbox has attracted attentions for its significance in preventing catastrophic accidents and guaranteeing sufficient maintenance. A novel fault diagnosis method based on the Ensemble Multi-Fault Features Indexing(EMFFI) approach is proposed for the condition monitoring of gearboxes. Different from traditional methods of signal analysis in the one-dimensional space, this study employs a supervised learning method to determine the faults of a gearbox in a two-dimensional space using the classification model established by training the features extracted automatically from diagnostic vibration signals captured. The proposed method mainly includes the following steps. First, the vibration signals are transformed into a bi-spectrum contour map utilizing bi-spectrum technology,which provides a basis for the following image-based feature extraction. Then, Speeded-Up Robustness Feature(SURF) is applied to automatically extract the image feature points of the bi-spectrum contour map using a multi-fault features indexing theory, and the feature dimension is reduced by Linear Discriminant Analysis(LDA). Finally, Random Forest(RF) is introduced to identify the fault types of the gearbox. The test results verify that the proposed method based on the multi-fault features indexing approach achieves the target of high diagnostic accuracy and can serve as a highly effective technique to discover faults in a gearbox machinery such as a two-stage one.